This application claims priority under 35 U.S.C. xc2xa7119 from Malaysian patent application serial number PI 20002854, filed Jun. 23, 2000.
The present invention relates generally to an improved method for sawing a moulded leadframe package into a plurality of integrated circuit units.
An individual integrated circuit or chip is usually formed from a larger base structure known as a moulded leadframe package or commonly called in the art as MLP. The MLP has a plurality of integrated circuit units arranged in rows and columns with the periphery of each integrated circuit unit being rectangular. Typically, the MLP is sawn or xe2x80x9cdicedxe2x80x9d into rectangularly shaped discrete integrated circuits along two mutually perpendicular sets of parallel lines or streets lying between each of the rows and columns thereof. Hence, the separated or singulated integrated circuit unit is commonly referred to as a dice.
One exemplary MLP saw includes a rotating dicing blade mounted to an aluminum hub and attached to a rotating spindle, the spindle being connected to a motor. Cutting action of the dicing blade may be effected by diamond particles bonded thereto, or a traditional xe2x80x9ctoothedxe2x80x9d type dicing blade may be employed. Many rotating MLP saw structures are known in the art. The present method is applicable to any MLP saw construction, so further structures will not be described herein.
MLP in the art usually contain a plurality of substantially identical integrated circuit units arranged in rows and columns. Two sets of mutually parallel streets extending perpendicular to each other over substantially the entire surface of the MLP are formed between each discrete integrated circuit and are sized to allow passage of a dicing blade between adjacent integrated circuits without affecting any of their internal circuitry. A typical MLP sawing operation includes attaching the MLP to a carrier, mechanically, adhesively or otherwise as known in the art, and mounting the carrier on a table of the MLP saw. A dicing blade of the MLP saw is passed through the surface of the MLP, either by moving the dicing blade relative to the MLP, the table of the MLP saw and the MLP relative to a stationary dicing blade, or a combination of both. To dice the MLP, the dicing blade cuts precisely along each street, returning back over (but not in contact with) the MLP while the MLP is laterally indexed to the next cutting location. Once all cuts associated with mutually parallel streets having one orientation are complete, either the dicing blade is rotated 90xc2x0 relative to the MLP or the MLP is rotated 90xc2x0, and cuts are made through streets in a direction perpendicular to the initial direction of cut. Since each integrated circuit on a conventional MLP has the same size and rectangular configuration, each pass of the dicing blade is incrementally indexed one unit (a unit being equal to the distance from one street to the next) in a particular orientation of the MLP. As such, the dicing blade and the software controlling it are designed to provide uniform and precise indexing in fixed increments across the surface of the MLP.
In the present practice, sawing of the MLP is done along a street on a connecting bar that joins a set of leads from one integrated circuit unit to another set of leads of adjacent integrated circuit unit. This practice generates a lot of heat that may cause considerable damage, solder melt and leads delamination have been reported rampant. Also, the excessive heat slows down the sawing process and reduces substantially the life of the dicing blade. Therefore, there arises a need for improved methods of sawing MLP that overcome the above drawbacks of the current practice.
Accordingly, one aspect of the present invention provides methods for sawing MLP that generate less heat.
Another aspect of the present invention provides methods for sawing MLP that cause less damage to the leads.
Yet another aspect of the present invention provides methods for sawing MLP that are faster and more efficient.
These and other aspects of the present invention are accomplished by,
A method for sawing a moulded leadframe package (1) into individual integrated circuit units (11), said integrated circuit unit (11) having a die-attach pad (12), a plurality of leads (13) and a connecting bar (14), said method comprising;
attaching said moulded leadframe package (1) to a carrier;
mounting said carrier on a table of a dicing saw; and
sawing said moulded leadframe package (1) along a street (15),
characterized by said street (15) being located on said plurality of leads (13).